A joint fishing agreement reportedly being discussed between China and the Philippines would further calm an old maritime sovereignty dispute while deepening friendship that was once thought all but impossible, experts in the region say.

Governments from the two Asian countries are talking about a tentative deal now after Chinese President Xi Jinping and his Philippine counterpart Rodrigo Duterte agreed to pursue it during a meeting in April, according to media outlets in Manila.

“If it will be actually reached, signed, implemented, that will signal not a milestone but a significant step forward in the relations between the two countries,” said Fabrizio Bozzato, a Taiwan Strategy Research Association fellow specialized in East Asia and the Pacific. “Sharing resources is not a light matter, light issue.”

The Philippines formally disputes Chinese fishing boat, coast guard and naval use of the South China Sea within its 370-kilometer-wide coastal exclusive economic zone.

But months after Duterte took office in 2016, the two leaders met to form a friendship that has seen both sides set aside the maritime dispute. As part of those stronger relations, China is rolling out pledges of $24 billion in aid and investment to help the Philippines develop.

Bitterness behind them?

China cites historical maps to back its claims to about 90 percent of the sea despite competing sovereignty assertions from Brunei, Malaysia, the Philippines, Taiwan and Vietnam.

FILE - Philippine President Rodrigo Duterte, front, walks with Chinese President Xi Jinping during a welcoming ceremony outside the Great Hall of the People in Beijing, China, Oct. 20, 2016.

Beijing and Manila sparred from 2012 to 2016 over fishery-rich Scarborough Shoal. The more militarily powerful China ended up taking control.

When Duterte visited China in late 2016 to break ice, Xi called for “stronger bilateral cooperation in fisheries” among other sectors, China’s official Xinhua News Agency said in October that year.

But a fishing deal may go too far, some scholars say.

The Philippines’ hands are “legally tied” constitutionally when it comes to signing formal fishing cooperation deals, said Jay Batongbacal, a University of the Philippines international maritime affairs professor. Any deal might be just a “modus vivendi,” he said.

“If it is within our EEZ (exclusive economic zone), it’s not an agreement, it should be a fishing permit,” said Antonio Contreras, political scientist at De La Salle University in the Philippines. Ideally, he said, “it’s not an agreement between equals, but it’s more like ‘I’m giving you permission to fish under my terms.’”

A more formal agreement might say which side can fish where, including access for both to disputed waters.

“Because there’s no actual agreement, then we’ll have the potential for flare-ups again,” Batongbacal said.

Elsewhere in East Asia, the Philippines signed a fisheries-related law enforcement agreement with Taiwan in 2015. Vietnam and Malaysia were working on a fishery deal last year.

FILE - An aerial photo taken from a Philippine military plane shows reclamation activities by China on Mischief Reef in the Spratly Islands in the South China Sea, west of Palawan, Philippines, May 11, 2015.

Message to other countries

China may hope the agreement shows goodwill to the other Southeast Asian countries with maritime claims, said Alexander Huang, strategic studies professor at Tamkang University in Taiwan.

It has angered the others by building up small disputed islets, in some cases for its own military use, and by declaring annual fishing moratoriums in the northern part of the 3.5 million-square-kilometer waterway.

“Probably China wanted to set up some kind of precedent so other countries can take reference to or think about those,” Huang said. “I don’t think [a Philippine deal] will be anything that’s related to the settlement of [a] sovereignty dispute. It will be seen as dispute prevention measures.”

China lost world court arbitration in 2016 to the Philippines over the extent of its claims. But it rejected the ruling. Since then it has sought peace with other claimants through bilateral deals and economic aid.

A deal with the Philippines would mean China “gets access to resources, they can send their people there and they look good nationally and regionally,” Bozzato said.

Risk of a raw deal?

As many as 1.6 million vessels from all countries combined fish the South China Sea, according to research under the China Program at the S. Rajaratnam School of International Studies in Singapore.

But Filipino fishing boats generally stay inside the 370-kilometer line and in the nearby Spratly Islands as traditional fishing grounds, Batongbacal said. Their boats are often too small or weak to test more distant seas.

Boats from China, Taiwan and Vietnam regularly fish farther out.

A fishing deal might effectively let Chinese vessels use the Philippine maritime claim without risk, even while no Filipinos venture into waters closer to China itself, some scholars fear.